Endoscopic surgery is becoming increasingly popular because it is a minimally invasive form of surgery, it is associated with less pain, and the patients can return back to normal work relatively early with minimal loss of working days.
In endoscopic surgeries, an endoscope is typically introduced into a body cavity via the natural opening of the cavity or, alternatively, a minute hole is made in the wall of the cavity through which the endoscope is introduced to visualize the interior of the body tissue cavity and to perform endoscopic surgical procedures. For the purposes of the present invention, the term “tissue cavity opening” shall be used to refer to a natural opening of a body tissue cavity opening, via which an endoscopic instrument is introduced. Additionally, the term “tissue cavity opening” shall be used to refer to an incision or hole made in the tissue cavity for passing an endoscopic instrument. For these reasons, endoscopic surgery is also referred to as “key hole” or “minimal access” surgery.
Endoscopic surgery is primarily related to a tissue cavity. Most endoscopic surgical procedures are carried out on an existing body cavity which is distended or “ballooned up” by filling the cavity with a suitable distending medium, which permits the inner lining of the tissue cavity to be visualized through an endoscope. Hysteroscopy, arthroscopy and laparoscopy are only a few of the routinely performed endoscopic procedures.
In its natural state, a tissue cavity is a collapsed structure with the cavity walls being in apposition with each other as if kissing each other. Accordingly, if an endoscope is introduced in such a collapsed cavity, no endoscopic visualization is possible unless the cavity is ballooned up by filling it with a transparent fluid. Such ballooning of the tissue cavity is called “cavity distension.” No endoscopic procedure can be performed if an adequate distension of the tissue cavity is not achieved and maintained. Cavity distension provides both endoscopic visualization and mechanical distension, which are necessary for the manipulation of endoscopic instruments.
Besides many other criteria related to patient safety and surgical accuracy, an efficient cavity distension is one in which the distending medium does not leak by the sides of an endoscopic instrument. If leakage occurs, the tissue cavity collapses and adequate mechanical separation of the cavity walls cannot be achieved and the mechanical separation cannot be maintained, thus making endoscopic surgery difficult or impossible. Accordingly, it is extremely important to prevent the leakage of the distending medium by the sides of an endoscopic instrument.
For a better understanding of the present invention, a brief description of the basic physics of cavity distension is provided below. Filling the tissue cavity with fluid enables distension of the cavity. Initially, more fluid is pumped than the amount which is extracted from the cavity and, ultimately, the inflow rate is fixed at a level where a desired cavity pressure and distension is achieved. This is termed distension by using “continuous flow irrigation.” However, a cavity can also be distended by using the less preferred “non continuous flow irrigation,” wherein the cavity is distended by simply instilling fluid into a cavity while there is no outflow tube. This distension by “non continuous flow irrigation” can also be termed “distension by utilizing a static type system.” In laparoscopic surgery, the abdominal cavity is only distended by instilling carbon dioxide by the static type of system. Irrespective of the type of distension technique utilized, i.e., distension by “continuous flow irrigation” or distension by using a “static type system,” it is important to avoid or at least minimize the leakage of the distending medium by the sides of the endoscopic instrument.
An endoscope is a cylindrical tube having an outer diameter ranging between 3 to 9 mm approximately. A typical endoscope has four channels. One channel allows passage of a fiber optic telescope while endoscopic instruments are inserted through a second channel. A third channel, also known as the “inflow channel,” is used for introducing irrigation fluid into a tissue cavity, the proximal end of this channel ending in a metal adaptor known as the “inflow port,” while the distal end of this inflow channel opens near the tip of the endoscope. The inflow port is connectable to an inflow tube which carries sterile irrigation fluid from a fluid source reservoir. A fourth channel, also known as the “outflow channel,” allows extracting the waste fluid out of the cavity, the proximal end of this channel ending in a metal adaptor known as the “outflow port,” while the distal end of this outflow channel opens near the tip of the endoscope. The outflow port is connectable with an outflow tube which transports the waste fluid from the cavity to a suitable waste fluid collecting reservoir. However, in the static distension system, the outflow port and the outflow channel are missing or not used in the endoscope, and either gas or fluid can be instilled via the inflow channel of the endoscope. A set of fiber optic bundles contained inside the telescope transmit light energy produced by an external light source. This light energy illuminates the walls of the tissue cavity. The image thus formed is carried via a separate set of optical pathways situated inside the telescope. A video camera attached to the eye piece of the telescope forms a clear endoscopic image of the cavity on a TV monitor. The surgeon has to continuously look at the TV monitor all through the endoscopic procedure.
A brief description of a distending medium leak occurring by the sides of an endoscope of the prior art is described below. The fluid of gaseous medium which distends a tissue cavity is pressurized and, thus, it may leak by escaping through a potential space located between the endoscope and the tissue cavity opening, if a liquid tight or a gas tight contact is not present between the endoscope and the tissue cavity opening. Such leakage is undesirable and, thus, the terms “cavity leak” and “cavity leakage” (which are used interchangeably) refer to leakage of a distending liquid or gas by the sides of an endoscope, including endoscopic surgical instruments that could enter into the tissue cavity through a cannula or which may be introduced directly (that is without a cannula). The surgical instruments could be shavers, endoscopic forceps, endoscopic scissors, endoscopic tissue retractors, probes and electrodes, among others. Thus, for the purposes of the present invention, the terms “endoscope” and “endoscopic instrument” are used interchangeably, and these terms are intended to include all surgical instruments whether passed directly or through a cannula.
The mechanism and causes of “cavity leakage” are different for different type of endoscopic procedures. Accordingly, a separate discussion for each type of endoscopic procedure is provided below.
In arthroscopic surgery, a trocar cannula is initially introduced into a joint cavity and subsequently the trocar is removed from the cannula to allow an endoscopic instrument to be introduced in place of the trocar. The trocar cannula consists of a trocar contained inside a cannula, which is a hollow rigid, usually metallic, cylindrical tube. The trocar is a long solid cylindrical rod, usually metallic, having a pointed or a relatively blunt distal end. A small incision is made in the skin overlying the joint cavity, and the trocar cannula is inserted into the joint cavity by using the pointed end of the trocar. The initial incision created by the pointed tip of the trocar is subsequently dilatated by the dilated proximal part of the trocar. The telescope is usually housed in a portal created in the manner just described. A separate portal may also be made in a similar manner to house an outflow tube via which waste fluid would be removed from the joint cavity. A shaver, especially for treatment of a shoulder joint, may also be passed via a portal incorporating a cannula as already described.
Alternatively, in certain situations such as the knee joint, a shaver may be directly introduced into the joint cavity without using the cannula. For this, a slit is first made in the capsule wall through which the shaver is directly inserted into the joint cavity. Especially at higher intra articular pressures, the distending fluid may leak around the sides of the shaver or around the sides of other endoscopic instruments inserted into the joint cavity. Such leakage is undesirable as it leads to a reduction in the intra articular pressure, which necessitates a greater inflow rate in order to maintain the same intra articular pressure. In addition, if a peristaltic pump is used, for example, on the inflow side, such increased flow rate could culminate in an increased frequency and amplitude of the cavity pressure pulsations caused by the peristaltic pump, which will ultimately lead to an increased turbulence inside the joint cavity. The cavity leak could also lead to a fluid leakage on the floor, it could also cause extracapsular extravasation of fluid, and it could also impede a surgeon from correctly calculating the total volume of fluid extravasation, as there is no reliable method of measuring the total volume of fluid which spills on the floor. The cavity leakage could also occur if two endoscopes having different outer diameters were interchanged.
In laparoscopic surgery, the carbon dioxide gas used for distending the abdominal cavity may at times leak around the sides of the endoscope, especially if two endoscopes having different outer diameters are interchanged. Such a leak can also occur if the initial slit given over the fascia, to facilitate the insertion of the trocar cannula, is relatively larger than required.
In hysteroscopic surgery, fluid might leak through a space present between the hysteroscope and the cervical os, especially if the cervical os is accidentally over dilated or if the cervical os is wide open right from the beginning of the surgery. The term “cervical os” refers to the natural opening of a woman's uterus. Such cavity leakage could make hysteroscopic surgery difficult as well as dangerous.
Methods for avoiding or minimizing cavity leakage are desirable as they would make the endoscopic procedures easier, safer and would also help in conserving costly distending fluid. A method for preventing or minimizing such leakage is to install a plastic or metallic sheath permanently over the endoscope. Such sheath must not be allowed to slip or to get detached from the endoscope. In physical terms, incorporation of the sheath results in an increase in the effective outer diameter of the endoscope, which reduces or avoids cavity leakage by developing a watertight or a gastight contact between the endoscope and the tissue cavity opening. However, it is impractical and difficult to use such sheaths and the result, in terms of minimizing or avoiding cavity leakage, is also unpredictable.
Further, if endoscopes must be interchanged during the course of an endoscopic procedure, it is inconvenient, from a practical standpoint, to remove and then install a sheath having a different outer diameter. The incorporation of the sheaths also restricts the maneuverability of the endoscope, thereby requiring greater force to move the endoscope in a to and fro, or rotary, motion.
Accordingly, a need exists for a system which would help in avoiding or minimizing the leakage of a gaseous or liquid distending medium through a space located between an endoscopic instrument and a corresponding tissue cavity opening, so that the maneuverability of the endoscopic instrument is not compromised.